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Volume 34 , Issue 1
January/February 2019

Pages 2530

In Vitro Study of Bond Strength Between Abutments with Different Degrees of Convergence and Crowns by Pre-Bonding Method

Liguo Zhao, MSc/Paul Weigl, Dr Med Dent/Yanyun Wu, Dr Med Dent/Yuanzhi Xu, PhD, DDS

PMID: 30695084
DOI: 10.11607/jomi.6717

Purpose: To investigate the optimal degree of convergence of the abutment with which the bond strength achieved by the pre-bonding method is comparable with that in direct bonding with a conventional degree of convergence. Materials and Methods: Abutments with 5.5-mm diameter, 5-mm height, 0.5-mm shoulder width, and three kinds of degrees of convergence (2, 4, and 6 degrees) were first designed by digital modeling. Their corresponding inner crowns were also modeled, and a gap of 40 μm was kept between the abutment and the inner crown. Thirty abutments and 30 inner crowns were then lathed out from a titanium plate (10 sets per degree of convergence). Six groups were defined in this study, according to the different degrees of convergence and bonding methods (direct bonding, pre-bonding) (n = 10 sets). The samples handled with direct bonding would be cleaned for reuse in tests with pre-bonding. Temporary cement was used as an adhesive, and the bond strength was tested in each set of samples. The comparison among the results was performed by the Kruskal-Wallis test. Results: The mean values of bond strength with direct bonding methods were 349.39 65.75 N, 316.49 54.22 N, and 277.49 56.96 N, and with pre-bonding methods were 279.35 48.58 N, 227.97 26.72 N, and 154.6 23.03 N, respectively (2, 4, and 6 degrees). No statistical difference was found among the values in direct bonding groups and, in pre-bonding groups, only the comparison between 2 and 6 degrees of convergence showed statistical significance (P = .000). Between different bonding methods, statistical differences were shown in abutments with 4 and 6 degrees of convergence (P = .006, P = .000), respectively. The bond strength with pre-bonding methods and 2 degrees of convergence showed no significant difference from that with direct bonding and 6 degrees of convergence. Conclusion: The bond strength was inversely proportional to the degree of convergence, and the bond strength of pre-bonding was lower than that of direct bonding with the same degree of convergence. When using the pre-bonding method, the bond strength between the abutment and inner crown with 2 degrees of convergence could be comparable with using the direct bonding method and abutments with conventional degrees of convergence.

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